System of motor control



Feb. 13, 1934. c. E. KILBOURNE SYSTEM OF MOTOR CONTROL Inventor 2 FiledAug. 6, 1932 v Charles E. Kilbourne Fig. I.

' in making the change.

ing trens -e- Patented Feb. 13, 1934 PATENT OFFICE SYSTEM OF MOTORCONTROL Charles E. Kilbourne, Schenectady, N. E, as-

signor to General Electric Company, a corpo ration of New YorkApplication August a, 1932. Serial as. serum 9 Claims. (o1. ire-27o Myinvention relates to systems of motor control, more particularly tocontrol systems for synchronous motors, and has for its object a simpleand reliable means for temporariiy chang: ing the connections of thefield windings of the motorso as to provide for increased fieldexcitation to take care of transient conditions.

In a copending application of Theodore Dreier and Charles E. Kilbourne,Serial No. 627,786, iiled- August 6, 1932, assigned to the same assigneeas this invention, there is described claimed broadly a system forchanging the field connections of a motor without loss of excitationwherein the field windings are switched from series to parallel ingroups of north and south pole field windings, this change made to giveincreased dynamic braking during stopping of the motor whereby the motoris brought quickly to rest. My present invention an i provement over theinvention t and Kilbourne application, whic made prior to my presentinrentio fore do not claim herein anything sr'wiri or tle-= scribed insai 1 eier and liilbourne a ication.

My present invention relates especmeans for changing the field ccnne toincreased feld excitation tempera-n short periods du ng operation of theis to pro ride for stability of operation of our t conditions, such assudden over loads or so after which the reccnnecteci as ice ore withoutinterrupting the ego-cra Lion of the tor for the continuance of normaloperation. .u is further object of my invention to provide means forchanging the connem tions without greatly lowering the noi pull outtorque of the motor at instant.

in carrying out my invention 1 provide switches and connections forchanging the connections of the field windings from series to parallelfor increased excitation including a resistance, and a lly series switchbetween the field windings whereby the field. windings are normallyconnected in series, together with. switches for establishing parallelcircuits around the field windings and the series switch, one oi saidcircuits including the resistance. after: which the series switch mayopened anti the resistance short circuited to provide parallelconnections for the field. windings for increased excitation.

The transfer of connections is thus made with out decrease in fieldexcitation at any instant such as would occur if the field circuit wasopened This system also provides for the change in the connections backto two sets or windings in series with each other series withoutinterrupting the operation o motor. My invention also comprehenos 6device for automatically changing to cc tions back. to series after apredetermined interval, together with load responsive tor initiallychanging the connections fro series to parallel and for initiatingoperation or me timing device.

For a more complete understanding vention reference should. be had tothe acco. partying drawing, Fig. l of which is a cliagre maticrepresentation of a system of motor Y trol embodying my invention, whileFi 2 simplified diagrammatic representation of switching means for thefield windings.

' to the drawing, 1 have shown my vention in one form as applied to thecentre alternating current synchronous rector cprising a tlireemiiasearmature wi" g mounted on. a stator member and. field a mounted on a.rotor ies shown ior the windings to this number of or division of field.windin s. The windings ll 3.2, constituting one o t set. excite poles oflike polarity such as no .ihese windings are in series with each 0.-

and 16 which are men it-ed on the rotor or soi the motor in insulatedrelation therewith. like manner the south pole windings l3 aconstituting other part or set are connects .1 series and to slip rings17 and iii also molest ed on the rotary shaft.

The field windings may be energised suitable direct current source ofsupply through conductors 29 and 21 and suitable switching mechanismincluding a switch 22 tor connecting the supply source to the conductors20 and 21, a series switch 23 for connecting the and upon occasionthrough two paralleling switches 25.

A clear understanding of the fundamentals o? my invention may nowperhaps best be had. reference to Fig. 2 showing it in its fundamentalaspects. During normal operation the windings are connected in seriesrelation with each other to the field supply source the switci 23 beingclosed and the switches 27 being open. In the event now that it is 1m 23and the field windings 11 and 12. It will be observed that theresistance 26 prevents a short circuit across the field supply source.

It will be observed that the establishment '0! these connections doublesthe excitation voltage applied to the field windings 13 and 14 sincethey are connected directly to the supply source, and also provides aclosed discharge circuit for these windings through the supply source sothat the switch 23 may be opened without damaging arcing. The excitationvoltage oifield windings 11 and 12, since they are short circuited, iszero, but because of the tendency of the machine circuits to holdconstant flux linkages by virtue of the magnetic energy stored in themachine, the total excitation of the whole field winding is notsubstantially decreased from the normal condition during the very shorttime 0! the switching operation. The switch 23 is next opened, afterwhich the switch 27 is closed to short circuit the resistance 26. Thiscompletes the connection of the field windings in parallel for doubleexcitation and applies double voltage to the entire winding. 1

In order to change the connections back to series the switches areoperated in the reverse order, i. e., first the switch 27 is opened,then the switch 23 is closed and finally the switches 24 and 25 areopened. In this manner the field connections can be changed as desiredfrom series to parallel orvice versa without interrupting the operationof the motor or without substantial decrease in the torque of the motorat any instant.

As shown, the various switches 23, 24, 25 and 27 are electromagneticallyoperated and my invention also comprehends a system 01 control for theseswitches as shown in Fig. 1. I

In starting the'motor, the supply conductors 20 and 21 are firstconnected to a suitable electrical supply source by a switch (notshown). A circuit is immediately established for the operating coil 30of the switch 23 whereby this switch is closed as shown in the drawingto connect the field windings in series with each other. This circuitfor the coil 30 leads from the supply conductor 20 through an interlockswitch 31 which is closed and the coil 30 to the supply conductors 21.The closing of the switch 23 at the same time closes its interlockswitch 32 and opens its interlock switches 33 and 34.

The circuits are now ready for the starting of the motor which iseffected by means of a push button switch 35. This switch closes thecircuit for the operating coil 36 which closes tour relay switches 37,38, 39 and 40, the circuit for the coil 36 leading from the supplyconductor 20, through the normally closed stop push button 41, thebutton 35, the interlock switch 32 which is now closed, and the coil 36to the supply conductor 21. The relay switch 37 closed by the coil 36establishes a circuit for the operating coil 42 which closes the triplepole switch 43, thereby connecting the motor armature to a suitablethree-phase supply source 44. The motor thereupon starts and acceleratesto approximately synchronous speed. It will be understood that the motoris provided with suitable starting means. such as a squirrel cagewinding (not shown) on its field member.

Upon its closing, the relay switch 38 closes a circuit for the operatingcoil 46 connected to operate a time relay switch 47. This time switchmay be of any suitable construction and is shown as connected to adashpot 48 whereby its closing movement is delayed, and to the armatureoi the coil 46 by means 0! a spring. After a predetermined intervaldetermined by the dashpot during which the motor accelerates tosubstantially its synchronous speed, the switch 47 closes a circuitthrough the relay switch 38 for the operating coil 50. This coil closesthe switch 22 whereby the motor field windings are connected to thedirect current supply source 19 in series relation with each other byreason of the fact that the switch 23 is clowd. .The motor is nowoperating as a synchronous motor. The closing of the relay switch 39 hasno immediate effect on the motor. The relay switch 40, however, closes aholding circuit for the coil 36, this holding circuit being across theswitch 32, and also across the push button 35 so that the push buttoncan be released immediately after the coil 36 is energized.

When it is desired to connect the field windings of the motor inparallel for increased excitation, the push button 51 is pressed wherebya circuit is closed for the operating coil 52, this circuit leading fromthe supply conductor 20 through the conductor 53, the relay switch 54which is closed concurrently with the closing of the switch 22,conductor 55, push button 51, coil 52 and thence to the supply conductor21. The coil 52 immediately closes a switch 56 in parallel with the pushbutton 51 which can be released.

The coil 52 also initiates the operation of a suitable timing device,such as described and claimed in the Stephenson Patent 1,699,125. Thistiming device is driven by a small electrical 1 motor 5'1 or othersuitable device, the energizing coil 58 of which is connected inparallel with the coil 52. Concurrently with the closing oi the switch56, the coil 52 moves a worm 59 driven by the motor into engagement witha worm 12s wheel 60. As shown a switch 61 is held in its closed position\by a pivoted latch 62. After a predetermined time interval, the timingmotor 5'? drives the worm wheel 60 around until a release pin 63thereupon engages the latch and trips it to release the switch 61 whichis biased to its open position by the coil 52. The coil 52 also biases aswitch arm 64 to the closed position. As shown the switch arm 64 has itsupper end provided with a hook engaging the upper 35 end of the pivotedcontact arm of the switch 61 so that the switch arm 64 is held in theopen position by the latch 62.

In order to provide for automatically energizing the coil'52 to connectthe field windings in 1 parallel, the circuit tor-the coil 52 may beclosed in response to the load on the motor. To this end a relay switch65 is provided in parellel with the push button 51. This switch isprovided with an operating coil 66 which is connected to a current coil67 in the armature circuit of the motor. Thus the coil 66 will beadjusted to close the switch 65 upon the occurrence of a predeterminedoverload. It will be understood, however, that if desired the switch 65may be disconnected 15 and me push button 51 used. Ordinarily the pushbutton will be used for stopping only, when the load responsive switch65 is provided.

The closing of the push button 51 or the switch 65 also establishes acircuit forthe operating coil fiewhlch coil closes the two relayswitches 69 and 7e. Thecircuit for the coil 68 leads from the switch clor es through the switch 61 and the coil 68 to the supply conductor 21.The switches t close a circuit for the operating coil ceding from thesupply conductor the relay switch 39 otuer step carried out by theenergizatlon l El is opening of its interlock h deenergizes the coil 30at the ".cties 24; close whereby the oediately opens to cgien the seriesoetween the two sets of field wind lugs. "l .e coil ll also closes aninterlock switch '25 end th reby establishes e circuit for the cm ii towhich. coil closes the switch. 21'? the supply conductor to, switch 39',conductor '13. switch 75, switch as which is now closed, a relay switch'27 and coil 76 to the supply conductor 21. The interlock switch "25also closes a holding circuit for the coil ll leading from the conductor'23 through switch 75, coil ll and switch 33 which is now closed to thesupply conductor 21. The two sets of motor fields are new comiected inparallel ,ior double excitation and will remain so connected until thetiming motor operates to open switch and. close the switch 64;.

After a predetermined. time for which timing device is set, the latch 62is released whereby the switch il is opened to deeiiergizc the coil to,and the switch. arm es is moved to the closed circuit position. toenergize the coil to through the conductor 83.. The switches and 70immediately drop open thus turning the control of coil 71 over to theinterlock. switch. The opening of the relay switch '2'? by the coil todeeuergizes the coil '75 whereby the switch 2? opens thereby opening theshunt circuit around the resistance 26. When the switch 27 opens, therelay switch '23 mechanically cone neoted thereto is closed and acircuit thereby closed for the coil 30. The coil 3c thereupon closes theswitch 23 to establish the series con" nection for the field windingsand also closes the relay switch 32 and opens the relay switches 33 andat. This circuit for the coil so leads from the supply conductor 2cthrough the conductor 83, the switch 82, switch '78 and coil to supplyconductor 21.

In the next step the switches 24 and open. the operating coil 71therefor having been deenergized by the opening of the interlock switch33. Preferably the switch 25 is arranged to drop open slightly beforethe switch 24 so that the resistance 26 is momentarily connected in thecircuit of the field coils to limit any inductive current due to suddenchange in current through the field windings. For example the switch 24may be'connected to its operating rod through a spring 84 as shown so asto be held closed until after the switch 25 has opened.

The closing of the switch 64 also energizes a relay coil 85 in theconductor 81 which coil opens aswitch 86 in the holding circuit for thecoil 52. The switch 86 is preferably provided with a suitable timingdevice such. as a dashpot 8! so that it is not opened until after theseries connections for the field winding have been established. Thedeenergization of the coil 52 allows the switches 56 and 64 to open andthe switch 61 to close while the worm 59 is removed from engagement withthe wormwheel and the motor 57 is deenergized. 'ihe wormwheel ispreferably reset with the pin 63 in a predetermined angular position asshown in the drawing as by a spring (not shown). lfhe timing mechanismis now reset ready for the next operation.

In the event that the time interval of the timing device is not longenough to take care of the overload, it will be observed that continuation oi the overload condition when the load responsive control isused will maintain the switch 65 closed and consequently the coil 52 isimmediately energized again for a repetition of the cycle. It shouldalso he understood that if desired the uutomatic time i'emovai can beeliminated when the load responsive device is used, the fieldconnections then being changed in response to the load.

The interlock switch 54 operated mechanically by the switch 22 isprovided with a spring con nection 88 with its operating rod so thatthis switch when once closed is held closed by the t,

spring until slightly after the field switch 22 has opened. This assuresthat the field circuit is opened through the contactor switch 22 in theevent that the motor is shut down. as by the pushing of the stop button41, when the field 1;

windings are connected in parallel with each other for increasedexcitation. When the switch opens, a switch 89 is closed to connect :1-discharge resistance 99 acrossthe field windings. The subsequent openingof the relay switch opens the circuit for the operating coil and thetiming motor 57.

vifhen the switch 43 is opened by the push button ll to stop the motor arelay switch 100 closed, which switch closes the circuit for theoperating coil 101 of a switch tea. The switch 162 is thus closed toconnect the resistors 1G3 across the armature circuit of the motor fordynamic mouse. To effect quick stopping with increased field excitationthe push button 4.1 is pressed along with the push button 51.

While 1'. have shown a particular embodiment of my invention, it willbeunderstood of course that I do not wish. to be limited thereto sincemany modifications may be made. and It therefore contemplate by theappended claims to cover any such modifications as fall within the truespirit scope of my invention.

What claim as new and desire to secure by Letters Patent of the UnitedStates is: r

l. The combination with a motor provided with at least two fieldwindings, anormally closed series switch between said field windings,parallel switches for establishing parallel circuits around said seriesswitch and the respective field windings, a, current limiting device inone of said parallel circuits, and means responsive to the load on themotor for effecting the operation of said switches in a predeterminedsequence.

2. The combination with a motor provided with at least two fieldwindings, a normally closed series switch between said field windings,parallel switches for establishing parallel circuits around said seriesswitch and the respective field windings, a resistance in one of saidparallel circuits, a switch for short circuiting said resistance, meansresponsive to the load on the motor for effecting the operation of saidswitches in a predetermined sequence, and timing means for controllingthe operation of said switches in the reverse order after apredetermined time interval.

3. The combination with a synchronous motor provided with at least twofield windings, a normally closed series switch between said fieldwindings, parallel switches for establishing parallel circuits aroundsaid series switch and the respective field windings, a resistance inone 01 said parallel circuits, a switch for short circuiting saidresistance, means for effecting a predetermined sequence operation ofsaid switches so as to first close said parallel switches, open saidseries switch and then close said resistance short circuiting switch, atiming device, and means operated by said timing device for operatingsaid switches in the reverse order after a predetermined time interval.

4. The combination with a synchronous motor provided with at least twofield windings, a normally closed series switch between said fieldwindings, parallel switches for'establishing parallel circuits aroundsaid series switch and the respective field windings, means responsiveto the closing of said parallel switches for opening said series switch,current limiting means in one of said parallel circuits and meansresponsive to the opening of said series switch for short circuitingsaid current limiting means.

5. The combination with a synchronous motor provided with at least twofield windings, a normally closed series switch between said fieldwindings, parallel switches for establishing parallel circuits aroundsaid series switch and the respective fieldwindings, a resistance in oneof said parallel circuits, a switch for short circuiting saidresistance, a control device for closing said parallel switches,interlock control means between said switches for effecting thesubsequent opening of said series switch and the c1os-' ing of saidresistance short circuiting switch in the order mentioned, a timingdevice, means operated by said control device for setting said timingdevice in operation, and means operated by said timing device forcausing the operation of said switches in the reverse order after a predetermined time interval.

6. The combination with a synchronous motor provided with at least twofield windings, a normally closed series switch between said fieldwindings, parallel switches for establishing parallel circuits aroundsaid series switch and the respective field windings, a resistance inone of said parallel circuits, a switch for short circuiting saidresistance, and means responsive to the load on said motor for effectinga predetermined operation of said switches so as to first close saidparallel switches, open said series switch and then close saidresistance short circuiting switch.

7. The combination with a motor provided with at least two fieldwindings, means for normally connecting said field windings in seriesrelation with each other, means responsive to the load on said motor forconnecting said windings in parallel relation, time element means, meansoperated by said load responsive means for initiating the operation ofsaid time element means and means operated by said time element meansfor reestablishing said series connections after a predetermined timeinterval.

8. The combination with a motor provided with at least two fieldwindings, a series switch between said field windings, parallel switchesfor establishing circuits around said series switch and the respectivefield windings, means responsive to the load on said motor for closingsaid parallel switches, means responsive to the closing of said parallelswitches for opening said series switch, a timing device, means operatedby said load responsive means for initiating the operation of saidtiming device and means controlled by said timing device forreconnecting said field 11 windings in series relation.

9. In a field control system tor a synchronous motor provided with atleast two field windings,

a series switch between said field windings, a timing device, aresistance, means responsive to 1 the load on said motor for initiatingoperation of said timing device and for closing parallel circuits aroundsaid field windings and said series switch, one of said circuitsincluding said resistance, means responsive to the closing of saidparallel cihcuits for opening said series switch, means responsive tothe opening of said series switch for short circuiting said resistance,means operated .by said timing device for reinserting said resistance,means responsive to the reconnection of said resistance for closing saidseries switch and means responsive to the closing of said series switchfor opening said parallel circuits.

CHARLES E. KILBOURNE. m

